Sorry but tracking the other dsf files I find for instance -43+171 in the -50+170 folder and would expect the missing dsf files in the same place.
As to being left out of the cut due to space contraints, this does not apply to XP 10 surely and the same dsf files also don't exist in XP 10, but no error is logged in the Xp 10 log.txt.
So that brings me back to my original question, what drives the loading of dsf files during the game start up?
My custom scenery add ons for both versions are identical so I leaning toward something within XP 11 that is calling for these dsf files that don't exist.